Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2006
Publication Date: 10/5/2006
Citation: Brown, A.E., Aldrich, J.R., Riddick, E.W., Holmes, W.E. 2006. The Identification of (-)-B-Caryophyllene as a Gender Specific Terpene Produced by the Multicolored Asian Lady Beetle. Journal of Chemical Ecology. 32:2489-2499.
Interpretive Summary: The multicolored Asian lady beetle (MALB) has received considerable attention in recent years for its usefulness as a natural enemy of aphids in various crops during the spring and summer. Unfortunately, it is also known for its annoying behavior of invading houses, during the fall and winter seasons, and forming in groups in attics and other secluded places. A compound was found and identified to be a component of the body odor produced by females but not males. This could prove significant and eventually lead to the identification of an aggregation and/or sex pheromone that could help us prevent the beetle for invading the home.
Technical Abstract: This work reports the development of novel techniques for characterizing volatile chemicals emitted by the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in an effort to identify semiochemicals involved in establishment and persistence of overwintering beetle aggregations. Volatiles emitted from live beetles were detected by using whole-air sampling and solid phase microextraction (SPME). Adsorbed volatiles were thermally desorbed and identified using gas chromatography-mass spectroscopy (GC/MS). By comparing chromatograms of volatiles emitted from live male and female beetles, a sesquiterpene, (-)-B-caryophyllene, was found only in the female beetles. The identity of (-)-B-caryophyllene was confirmed using NIST Library searches, comparing retention times with those of known standards and by higher resolution magnetic sector GC/MS. Although SPME trapping detected a wider array of compounds compared to whole-air sampling, the latter sampling method is better suited for automation. Unattended automated sampling is required for the continuous measurement of targeted compounds under dynamically changing incubation conditions. These incubation conditions, mimicking natural overwintering conditions, are essential to our long-term goal of using this technology to detect and identify the aggregation pheromone of H. axyridis.